On the one hand, cleaning nozzles should already be capable of operating under low working pressures, for example from approximately 0.5 bar. On the other hand, the nozzles should not have too high a rate of rotation when higher operating pressures are used, for example pressures above 20 bar. A rate of rotation of the nozzles that is too high impairs the cleaning effect.
A nozzle that rotates in operation and is driven by a fluid is known from BE-A 720 408. The nozzle has a cylindrical housing in which a hollow shaft is rotatably supported by ball bearings. The upper end of the hollow shaft is arranged with an axial connection which serves for feeding a fluid. On the lower end of the shaft, a nozzle head is provided, which rotates with the shaft. In the nozzle head, a distributor pipe is provided which communicates with the shaft. The distributor pipe is arranged on both sides of the shaft, transversely to the shaft, and carries on its ends in each case transversely branching-off orifices. The rotatably supported distributor pipe carries a gear wheel which rolls off on a gear wheel fastened to the housing. Thereby, the orifices are also made to rotate about the horizontal distributor pipe axis, in addition to their rotation about the vertical axis.
A turbine which is torsionally joined with the hollow shaft serves as the drive. The turbine has a runner with several obliquely set blades. The runner is arranged in a housing which has five face-side oblique bores for fluid inlet. This guides the fluid into the space between the turbine and the housing in such manner that the rotating turbine is also self-braked with increasing operating pressure, and its rate of rotation does not rise above a certain limit.
The nozzle has a mechanical structure, especially through the separate turbine. If the fluid is not entirely pure or for other reasons contains particles, the particles cannot be deposited between the turbine and the housing and impair the functioning of the nozzle. The significant portion of the fluid that is branched off for drive purposes is emptied through the bottom of the housing and is not led to the orifices.
A further rotating nozzle having a hollow shaft rotatably supported in a housing with a turbine torsionally joined therewith is known from EP 0 645 191 B1. The bearing of the shaft is obtained by a radial bearing surface on an axial bearing bore and an axial bearing surface. The turbine is set into rotation, or maintained in rotation, by an injector. The axial bearing surface acts as a friction brake controlled by the fluid pressure. It acts against the drive force generated by the fluid, with which the turbine is acted upon. Thereby, and over a broad pressure range, an excessively high nozzle rate of rotation can be prevented.
The nozzle has proved successful in practice. Certainly, with increasing fluid pressure, increased friction can occur on the friction brake, and accordingly there will be wear. Long term wear resistance can be obtained by choosing a suitable material, in the present case PTFE. However, the construction of the nozzle is somewhat complicated.